Vertical discrepancy and microleakage of laser-sintered and vacuum-cast implant-supported structures luted with different cement types

SEM evaluation of the precision of fit of CAD/CAM zirconia and metal-ceramic posterior crowns

“…This research attempts to compare the accuracy of fit of three different CAD/CAM zirconia systems and conventional metal-ceramic tecbnique, and vertical gap was measured to permit comparison with previous studies 8,9,15,17,18,[21][22][23] . The data obtained in the study support the partial rejection of the null hypothesis because differences in marginal fit were shown among the groups, however no differences were observed between external and internal marginal discrepancy values.…”

“…Several direct and indirect methods are available for analyzing the marginal and internal adaptation of fixed prosthodontics restorations. Some methods include perfilometry 14) and microfiltration with dyes, whose main drawback is the subjectivity inherent in using semi-quantitative measuring scales 17,18,30) . Direct viewing with external measurements has the advantage of being noninvasive and is, therefore, useful to determine the precision of fit of the restorations 7,15,29) .…”

“…Some controversy has arisen around the measurement instruments, thus an optical microscope 20,24,28,31) , digital micrometer 36) , laser microscope 33) , or image analysis system [7][8][9]11,15,20,33) , have been proposed as an alternative to SEM 15,[17][18][19]23,37) . While some authors have found the precision obtained with an optical microscope and SEM to be similar 37) , other authors could not demonstrate which was the best method 15) .…”

“…Prior to SEM evaluation, samples were gold coated under vacuum (K550X, Emitech Quorum Technologies, Kent, UK) to render them electrically conductive. Due to the morphology of the crowns, the samples were mounted on a customized metallic support at an angle of 25 degrees in order to situate the interface perpendicularly to the optical axis of the microscope, thus guaranteeing repeatable projection angles 17,18) . To standardize the marginal analysis, the measuring areas were previously marked with an indelible marking pen (Lumocolor permanent, Staedtler Mars, Nürnberg, Germany) at the same point in the middle of the buccal and lingual surfaces for each crown [7][8][9] .…”

“…The data were captured and the images digitized using the software INCA suite 4.04 (Oxford Instruments Analytical, Oxford, UK). Previous studies 9,[17][18][19][20] were considered regarding the number of measurements, therefore to increase the number of measurements per specimen, the images were edited using design software (Adobe Photoshop CS6, Adobe Systems, San Jose, CA, USA) to produce lines that were parallel to the original, and up to 29 lines per side were added on each SEM image. To increase the reliability of measurements, each line was measured three times and their average values were taken 17) .…”